In U.S. patent application Ser. No. 204,327 filed June 9, 1988, for "Method of Making a Cathode From Tungsten and Iridium Powders Using a Barium Peroxide Containing Material as the Impregnant" by L. E. Branovich, G. L. Freeman, B. Smith, and D. W. Eckart and assigned to a common assignee and with which this application is copending, there is described and claimed a method of making a long life high density cathode that uses as the impregnant barium peroxide alone, or a mixture of barium peroxide with iridium, or a mixture of barium peroxide with osmium, or a mixture of barium peroxide with rhodium. Although desirable in many aspects, the difficulty with the method of that invention is that the chemical reaction is not rapid enough.